How Earth, but not Venus, formed its tectonic plates

Ars Technica : So far, Earth appears to be unique in the universe in that it not only supports life but also exhibits plate tectonics. Now researchers think the two phenomena may be connected. In a paper published in Nature, they compare Earth and Venus, which are about the same size and composition. They modeled the formation of the two planets, starting with both as hot, mushy conglomerations of tiny particles of rock. Over a time span of 1 billion years, each planet’s mantle caused surface material to sink, or subduct. Earth’s crust tended to harden and crack into distinct pieces at those subduction zones, while Venus’s crust, kept warm and soft by the planet’s higher temperature, continually repaired itself. It may be Earth’s tectonic activity, however, that has allowed life to emerge. As one plate slides under another, it pushes carbon down into the mantle, preventing it from building up in the atmosphere and becoming toxic, as has happened on Venus.